Discovered quite a while ago (1993; [PMID 8506290]), this mutation originally found in Finnish and Swedish Laplanders results in a mild familial (and dominant) form of erythrocytosis. Lifespan is unaffected, and in fact, the higher hematocrit levels (based on having more red blood cells) appears to predispose these individuals to perform better in endurance sports. Perhaps the best known example of this is the Olympic cross-country skier, Eero Mantyranta.